Research data supporting Zintl Phases K4–xNaxSi4 (1 ≤ x ≤ 2.2) and K7NaSi8: Synthesis, Crystal Structures, and Solid-State NMR Spectroscopic Investigations

FID and Fourier-transformed 29Si and 23Na solid-state NMR data for K3NaSi4 and K7NaSi8; CASTEP density functional theory (DFT) calculation txt file containing input and outputs, especially NMR shielding and nuclear quadrupole coupling values for K3NaSi4 and K7NaSi8